MEXICO CITY -- It took a Facebook friend to blow the whistle on Paul Torres, a self-described endurance runner. The 36-year-old stockbroker posted a picture of himself at the finish line of Sunday's Mexico City Marathon and he barely looked fazed. There was no sweat permeating his attire or dripping down his face. His hair was perfectly parted and combed.

Torres didn't run the complete marathon. In fact, he jogged only the last mile or so to cross the finish line.

Under the early morning darkness, Torres drove to Zócalo -- Mexico City's historic center that dates back to the Aztec empire -- with his brother, intent on participating in the race along with close to 30,000 others. His brother dissuaded him at the last minute, because he had recently inked a large tattoo -- a tribal design, he said -- on his back. So he went home. But the thought to take a selfie crossing the finish line creeped in, and several hours later, he returned to cheer his brother on.

"I watched my brother toward the end and I took advantage of [having my bib with me] to cross the finish line and pick up a medal," Torres said in a phone interview with ESPN.

According to race officials, Torres was one of 3,090 runners disqualified amid allegations of course cutting. Many if not all were missing times at checkpoints. The mass cheating comes on the heels of last year's race, when 5,806 participants -- nearly one in five -- were deemed ineligible.

All summer long Torres had posted on his marathon preparation. The potential embarrassment, coupled with the marathon's lax security, resulted in him waltzing over to the final bend of the course, heading into Estadio Universitario UNAM.

"Unfortunately, it's true," Torres said of his cheating. "It happened and I have to own up to it. What's done is done.

"I got [the tattoo] done 15 days before the race, and so I couldn't sweat on it, I couldn't run. And I wasn't sure I could run the race itself."

Since the 2013 edition, Mexico City Marathon finishers got a medal with a letter. Sunday's edition capped the 'O.' ESPN Mexico via @MaratonCdMx

Despite the thousands whose times had to be scrubbed from the official results, race organizers called this year's edition a success.

"We had an increase in the number of runners who finished this year," said Horacio de la Vega, director general of Mexico City's government office in charge of sports, INDEPORTE, during a postrace media conference on Tuesday, when announcing the race's official results.

Though the eradication of cheating was a key talking point following last year's debacle, race officials still expected to inch closer to IAAF gold label certification, the most prestigious level a race can receive, which would place Mexico's event at the level of the Boston or New York City marathons. To qualify for gold level status, a race must have elite runners from at least five different countries, as well as television coverage or online streaming available to the public, sophisticated anti-doping controls, and a big screen at the venue's finish line for spectators to follow along, among other requirements.

One of the motivations for course cutting is the commemorative medals the city issued since the 2013 edition of the marathon. Each race since then has delivered a medal with a letter on it. After Sunday's, a finisher of all six races would have spelled the word "MEXICO." To curb cheating, race organizers announced all six replica medals would be available to buy at this year's venue as well as online, so non-competitors and runners alike could complete their collection regardless of whether they were signed up for this year's race.

The race's director, Javier Carvallo, also warned that repeat offenders would be permanently banned.

"There was a communication campaign in which we enticed runners to run the complete route, to run the marathon from start to finish," Carvallo told ESPN Mexico's Javier Rosas. "To those who have repeatedly [cheated], we'll penalize them through the federation and not allow them to run in any more races in Mexico City.".

"¿Ya se cansaron? (Are you tired?) Running team", a Facebook watchdog group, was quick to signal those who engaged in dishonest conduct, despite the measures. Last year, the group caught the eye of news outlets for uncovering public figures who cheated in the race. Torres' Facebook friend messaged the group.

"These people think that just because they paid the race fee, they're entitled to a medal," said one of the administrators of the group, who requested anonymity due to threats after exposing would-be cheaters. "They get angry when you expose them. I've had people threaten to find me, beat me up, or worse."

Though members of the group engage in active sleuthing after the race, the bulk of submissions ironically come from friends and followers of the offenders. This year, more than 1,000 submissions were made, according to the watchdog group. Reaction to perceived self-aggrandizing posts on social media are often motivators for whistleblowers, and possible cheating cases are uncovered when the runner's bib number is entered into the race's official app or website. Irregularities such as missed checkpoints or unrealistic finish times pop up.

"It's funny, we usually find out about cheaters from their friends, who are sick of them clogging up their feeds with lies," said the ¿Ya se cansaron? group administrator.

Still, legitimate finishers of the Mexico City Marathon, like 31-year-old Lilia Garduño, believe posturing for social media has been a detriment to the race environment. As she entered the race's final stage, the glut of people near the finish line caused problems.

"It was very challenging. I was already exhausted, and I had to avoid people who were taking selfies and walking around," Garduño said, adding she noticed many finishers didn't look tired or even sweaty. "It was so crowded, I almost didn't see the finish line."

For Torres, perceived pressure from social media was definitely a factor.

"I like to post major life achievements, and I felt like people were expecting me to [publish something] after the race. It felt easy," he admitted. "But I learned my lesson. Posting that on social media, which is usually a good thing for me, came back to haunt me."